This invention relates to a self-sealing pneumatic tire with puncture sealant properties and a method for manufacturing the tire. The concept of a tire with puncture sealant properties is old and the prior art is replete with various methods and combinations for obtaining a puncture sealant tire and a puncture sealant composition. These prior methods, constructions and compositions all have the final goal of obtaining a tire that exhibits puncture sealing properties when a sharp object, such as a nail, punctures the tire.
Examples of such teachings go back to the early 1900's (See U.S. Pat. No. 1,601,013; 1,977,281 and 1,419,470) wherein relatively simple disclosures were made to provide a tire with a strip of raw, unvulcanized rubber which, it is stated, would have puncture sealing properties. Later teachings relate to more sophisticated tire constructions, sealant compositions and methods wherein a sealant material is encased or encapsulated in or between calendered layers (see U.S. Pat. Nos. 3,048,509 and 2,877,810).
All of these teachings have had drawbacks which have led to the commercial unacceptability of the compositions, methods and constructions. For example, the teaching of providing a tire with a layer of unvulcanized rubber has been unsuccessful due to the fact that the unvulcanized rubber would become displaced during operating of the tire and would become ineffective as a sealant material on extended operation of the tire. The more complicated structures wherein the sealant material was encased in a vulcanized material were expensive to manufacture, created other problems due to the additional weight required in the tire and did not have adequate sealing properties. The present invention overcomes the drawbacks of all of the prior art.
The demand for a self-sealing tire has been renewed by the emphasis on the elimination of a spare tire in a passenger car and energy conservation programs. A major U.S. automobile manufacturer has taken the position that a tire must have self-sealing properties in order for the elimination of a spare tire in a passenger automobile to be seriously considered.
The Applicant has previously disclosed (Ser. No. 737,884, filed Nov. 2, 1976, issued as U.S. Pat No. 4,140,167 and Serial No. 615,266, filed Sept. 22, 1975, issued as U.S. Pat. No. 4,089,360) a tire with a layer of irradiation degraded material which is tacky or gummy (a low viscosity) wherein the material is degraded prior to assembly into the unvulcanized tire. This prior method and construction was only possible when the degraded layer was laminated with another undegraded layer which permitted its handling during tire building (its tacky, sticky nature and lack of strength made it unhandable alone) and enabled it to retain its integrity during the vulcanization operation wherein high pressures are applied to the tire which would displace the layer from its desired location. As will be explained later in greater detail, this invention provides for the irradiation of the degradable material after the tire is vulcanized so that during tire building and vulcanization the material is easily handled as it is of a high viscosity. This has not been taught by the prior art.
The prior art also has taught a method wherein a sealant layer is applied to the inner periphery of a tire. This method includes the cleaning of the inner surface of the unvulcanized tire by elaborate, expensive equipment and the application of the sealant material to the inner periphery of the tire, again by elaborate, expensive equipment. The method of this invention eliminates the necessity for such elaborate equipment.
This invention provides an uncomplicated, inexpensive construction and method for obtaining a self-sealing tire. It is an object of this invention to provide a pneumatic tire with a lightweight, uncomplicated, inexpensive puncture sealing member.
It is another object of this invention to provide a sealant layer with a blend of polymeric materials that, when combined, yield sealant properties with each of the polymeric materials contributing a different characteristic to the layer. The acceptable sealant properties of the layer will not be realized one polymeric material alone, the combination of properties is required.
It is another object of this invention to provide a simplified, inexpensive method for manufacturing a tire with self-sealing or puncture sealant properties wherein certain sealant properties are provided by a material that is easily handled during building and vulcanization and that is converted by irradiation after the tire is vulcanized. The tire construction and method of this invention meet the objectives set out above.